Add set16 function

include/vm_segment.h

@@ -58,6 +58,7 @@ extern int vm_segment_copy_buf(vm_segment *, const vm_8bit *, size_t, size_t, si
 extern int vm_segment_fread(vm_segment *, FILE *, size_t, size_t);
 extern int vm_segment_read_map(vm_segment *, size_t, vm_segment_read_fn);
 extern int vm_segment_set(vm_segment *, size_t, vm_8bit);
+extern int vm_segment_set16(vm_segment *, size_t, vm_16bit);
 extern int vm_segment_write_map(vm_segment *, size_t, vm_segment_write_fn);
 extern vm_16bit vm_segment_get16(vm_segment *, size_t);
 extern vm_8bit vm_segment_get(vm_segment *, size_t);

src/vm_segment.c

@@ -303,3 +303,28 @@ vm_segment_get_map_machine()
 {
     return map_mach;
 }
+
+int
+vm_segment_set16(vm_segment *segment, size_t addr, vm_16bit value)
+{
+    vm_8bit lsb, msb;
+    int err;
+
+    lsb = value & 0xff;
+    msb = value >> 8;
+
+    // This data needs to be saved in little-endian order; e.g. if we
+    // get $1234, then we need to store it as $34 $12.
+    err = vm_segment_set(segment, addr, lsb);
+
+    // If the previous set() worked out, then let's try it again with
+    // the msb.
+    if (err == OK) {
+        err = vm_segment_set(segment, addr + 1, msb);
+    }
+
+    // If err != OK above, we will just return the err code. If err was
+    // OK, but is not OK after the msb set, then we'll return with that
+    // code.
+    return err;
+}

tests/vm_segment.c

@@ -174,3 +174,9 @@ Test(vm_segment, get16)
 
     cr_assert_eq(vm_segment_get16(segment, 0), 0x1234);
 }
+
+Test(vm_segment, set16)
+{
+    vm_segment_set16(segment, 0, 0x2345);
+    cr_assert_eq(vm_segment_get16(segment, 0), 0x2345);
+}